EXHIBIT 5

November 28, 2001

Archstone-Smith Trust
7670 South Chester Street, Suite 100
Englewood, Colorado 80112


Ladies and Gentlemen:

         We have acted as counsel to Archstone-Smith Trust, a Maryland real
estate investment trust (the "Trust"), in connection with Post-Effective
Amendment No. 1 to the Registration Statement on Form S-3 (File No.
333-44639)(the "Registration Statement"), filed today with the Securities and
Exchange Commission (the "SEC"), with respect to the assumption by the Trust of
the Dividend Reinvestment and Share Purchase Plan (the "Plan") of Archstone
Communities Trust, a Maryland real estate investment trust ("Archstone"). The
Trust is making such filing as successor issuer to Archstone pursuant to Rule
414 under the Securities Act of 1933, as amended.

         As counsel to the Trust, we have examined originals or copies certified
to our satisfaction of the Trust's Amended and Restated Declaration of Trust and
Amended and Restated Bylaws, resolutions of the Board of Trustees and such other
Trust records, instruments, certificates and documents and such questions of law
as we considered necessary or appropriate to enable us to express this opinion.
As to certain facts material to our opinion, we have relied, to the extent we
deem such reliance proper, upon certificates of public officials and officers of
the Trust. In rendering this opinion, we have assumed the genuineness of all
signatures, the authenticity of all documents submitted to us as originals and
the conformity to authentic original documents of photostatic copies.

         Based upon and subject to the foregoing and to the assumptions,
limitations and conditions set forth herein, we are of the opinion that, upon
completion of the Trust Proceedings, the Trust's common shares of beneficial
interest, par value $0.01 per share, when issued and delivered in accordance
with the Trust Proceedings and the Plan, will have been validly issued, fully
paid and nonassessable.

         We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement.

                                                Very truly yours,

                                                /s/ MAYER, BROWN & PLATT